Counterboring tool



Dec. 24, 1940. Q Q HED|N 2,226,226

COUNTERBORING TOOL Filed Oct. 10, 19159 v Patented Dec. 24, 1940 OscarC.Hedn, Minneapolis, Minn.; assig'rr tol f The Weldon Tool Company,Cleveland; Ohiov a f corporation of Ohio Application october 10,1939,seriaiigoioggg@ 9 Claims.

, This invention relates to` improvements in pilots forfmetal cutting.tools with which al pilot is o r canbe used, particularly tools of thecountercutting type,s uch as reamers and counterbores. The inventionhasfound valuable application in a tool of the counterbore type.

Objects of the invention are: To so detachably mount the pilot thatpilots of different diameters can be quickly substituted, and to providea character of `mount which cannot becomey loosened in use and whichwill prevent such movements of the pilot as will mar or dull the Icutting ends of the tool, Oras will allow the pilot to assume eccentricpositions.

I -am aware that various attempts have been made to provide removablepilots but', insofar as I know, there exists no detachable pilot whichis entirely satisfactory..

.In some cases the pilot hasbfeen made ref movable by providing it Vwitha small shank which is inserted in an opening in the stern of the tool,wherein it is locked by a sety screw. When sucha pilot is in operativeposition the rear or innerfend of the `pilot bears against the ends ofvthe cutting lips. This type of pilot becomes loose andV vibrates orchatters,vand the inner end surface of the pilot can'chew up or mar ordeface the cutting lips. When this inarring occurs during use ofr alarger size'pilot, and onewishes to use the tool with ya smaller sizepilot, it is found thatv the cutting tool hasbeen so chewed up or marredthat it is necessary to re-sharpen the same, This takes timeandneedlessly shortens thel life 4of the cutting part of the tool.Insofar 'as I am aware, in allA of the manufacturing tools which have,had detachable pilots, it vhas been L,necessary to use set screws orthe like for holding them in place.v The main objection is that thosepilots work loose, with the results above'mentioned.' The videal pilotlmust be rigid, ,and I have provided this rigidity in a detachable pilot.

An important 'feature of my invention consists in providing a mount forthe pilot which is of one piece with the tool, that is, integraltherewith.v

TheI mount is of one piece or integral with the stem, as distinguishedfrom being separable w therefrom. Another feature is the provision of atapered mount not necessarily of one piece, with the tool.

In my invention I turna tapered extension at the end of the tool whichtapersconvergently in boring direction, and then Il form a correspondingtapered opening in the pilot. Each pilot of a series of pilots has adiierent outer diameter but -has the same diameter or dimension oftaper, so

(o1. 'ivomi y that each fone'willfit `one and the same integral taperedextension.; l

yl'eatures'j c'nlhtloe, invention include: the use of apilot-mountingextension which is of one piece l with the tool; the'useof a tapered mount, whereon the ypilot is frictionally held so that itcan be loosened by a slight otap; the use ofa cylindrical mount of'onefpiece .with the tool; the use of screw l@threads to ,secure thepilot to a mount which is integral. with 'the tool; the scheme of thesubstitution Lof pilotso'f different diameters on one andthesamelamount; vand all details of construction sh'flivvnl...A Y,

.O jects', vfeatures and advantages of the in,-r fventionwill kbesetforth in the specification and irl Said-drawing; Figurelfis anelevation cfa counterbore tool showing my inventionapplied'thereto andshow'- ing the, toolfin nterboring .position in relation to thewok; I

Figure Z'isjan enlargedsection of the lower .part "of' the' k tool withmy invention applied thereto; l .Figu res' 3,' 4 *and 5 are sections,respectively, of pilots'of' different outside diameters, any one ofwhich pilots can be applied to one and the same pilot mountof `thisinvention; v.ligure isfan enlarged section of a modification showingvthe pilot attached by screw threads; ':Figure j lis a section ofanother modification showing' thepilot vheld on a cylindrical mount;

' ,Eigurevis anfaxiallsection of a centering or sharpepingpilot.' f

my finventionas applied to a counterbore tool haVmgtWolips only; but itwill be understood 'that` the invention mayl be applied to any tool onwhich a'pilotcan be used or is needed, to pro.- videfnieanswhereby a4detachable pilot is unfailingly rigidly centered for performing itsfunction and .yetis quickly 'and easily removable so thatpilots f otheroutside diameters can be .substitutedf on fone andthe same mount.

'Thenunieralfl lindicates the shank of the tool andfgthe Irnneral 2indicate the cutting lips. Nun 1`l"=.rals A34 indicate the cutting edgesof the lips. Atfthe' upper, endof the tool is a centering depression v5fc :jorresponding to a similar depression atthe opposite'endof. the tool,as hereinafter described. means of these depressions the toolcan"'againv be supportedfor operations which will belaterdejs'c ri b ed.v

.jRlef'erijing'now;` o'Figure 2, a salient feature of 55 15drawingforming.apartlof this application, and

my invention is the provision of a pilot support or extension which isof one piece with the stem I, and which is turned and/or ground as thestem is turned and/or ground so that perfect centering can beaccomplished. This extension is generally indicated by the numeral I0and it is noted that it is tapered convergently in boring direction. Thepilot element per se is indicated at II and has a correspondinglytapered opening which has an accurate t with said projection so thatgood frictional contact is obtained, which alone secures the pilot inposition on the projection or extension I0. It is desirable to have theinner end or surface I2 of the pilot II spaced from the cutting edges I3of the lips 2, and it is desirable to always maintain this relationafter sharpening of the lips has occurred, which operation shortens thelips in an axial direction (see dot-and-dash lines I3' roughlyindicating the position of the cutting edges after sharpening). If it isdesired to maintain the predetermined special relation between the faceI2 and edges I3, the mount element is also ground, and so that the sametaper is maintained. For this purpose the tool is centered in thegrinder by means of the centers 5 and I4.

Figures 3, 4 and 5 show sectional views of pilots of differentdiameters, said diameters being respectively indicated by the letters A,B, C. In these figures it will be noted that the internal diameter ofthe conical opening indicated at D remains the same as the diameter D'(see Figure 2) of the tapered projection Ill. The result is that eitherof the pilots respectively indicated at I6, I1, I8 can be frictionally,immovably, rigidly held on the projection I0 of Figure 2. For ease ofmanufacture, of course, it might be considered most convenient to makethe pilot extension cylindrical, and Figure 7 shows such construction.

The important feature is the making of the pilot extension I0 or itsequivalent, of one piece with the stem I to assure rigidity, and so thatthe mount can be machined with the stem and can be re-ground to maintainthe proper relations between a pilot mounted upon it,and the cuttingedges of the tool as the cutting edges are sharpened back in an axialdirection.

To further define the meaning of the expression of one piece with, asused to describe the character of the extension upon which the pilot ismounted, it may be said that the most practicable way to form theextension is by turning during manufacture. However, if the tool iscast, then of course the extension should be formed by casting and wouldbe of one piece with the shank. It is conceivable that the extensionmight be welded in place, and if it were this would be another way ofobtaining a rigid, non-removable support for the pilot. These ways ofobtaining this rigidity are mentioned to make clearer the meaning of theterms of one piece with or integraL By making this tapered extension ofone piece with the shank or with the tool a rigid mount is obtained.This tapered extension may be called a sub-pilot, and upon thissub-pilot can be driven a master pilot of the desired outside diameter,this'master pilot having, as before mentioned, a tapered hole whichpermits it being driven into frictional engagement with the sub-pilot ortapered extension. Thus, there is here combined all the virtues of thesolid type of counterbore with the advantage of interchangeability ofpilots. As an extreme example, consider several screws, all of whichhave heads one inch in diameter but in each of which the shank has adiameter difering from that of the other, for example, ranging indiameter from 5/gths to lths of an inch. To do counterboring for theheads of these screws whose shanks vary in diameter there wouldordinarily be required as many counterbores with solid or integralpilots as there are different diameters of screws. Thus, it can be seenwhat advantages accrue from having a counterbore with interchangeable orreplaceable ilots.

p My invention gives a construction which has a maximum strength andrigidity and more nearly approaches the solid type pilot than any otherdevice known to me.

By the scheme herein or method of manufacture constant concentricity ofpilot and counterbore diameter is assured. The taper of the sub-pilot isground at one and the same time as the outside diameter of thecounterbore proper. The master pilots are easily made accurately,with-their outside diameter concentric with the axis of the tool. It isto be noted that lack of concentricity between pilot diameter andcutting-lip diameter is the most frequent cause of pilot breakage.

Another advantage of the present invention resides in the fact that thetaper can be ground so as to follow back as the cutting ends of the lipsare ground farther and farther back from their position when the tool isnew. As the lips are ground back in sharpening, the tapered extensioncan also correspondingly be ground back so that the inner end of thepilot, that is, the end which is nearest the lips, can always be made toassume a desired predetermined spaced or other relation with the cuttinglips. However, by the use of this invention, even though the inner endof the pilot AWere against the cutting lips, there would be nochattering with marring or dulling of the tool, because there ispositively no relative movement of the pilot. y

In Figure 6 I have shown a modication in which the sub-pilot or pilotmount or projection 'is threaded as at 20, and the pilot 2| iscorrespondingly threaded. In this case two methods may be employed forthreading the sub-pilot: (a) the threads may be cut before the tool ishardnened, or (la)` the threads may be ground thereon after hardening.Then as the cutting lips are sharpened back, the pilot is simply screwedon lfarther.

In Figure 7 I have shown a modification in which the sub-pilot or mount24 is cylindrical, rather than tapered.4 In this case the master pilotor part 25 has a slightly under-sized hole and the pilot 25 is eitherpressed or shrunk, or has a driven t with the extension. In this case,.as the cutting lips are sharpened back, means must be so exerted as topermit proper spacing l between the elements.

Although the greatest number of advantages of this invention accrue fromhaving the mounting extension for the pilot of one piece with the tool,I believe I am also the first to provide a sub-pilot which is integrallyattached to the tool and which has a surface which convergently tapersin a directionA away from the end of the tool and on which taperingsurface a pilot is Secured frictionally, so that all that is necessaryto remove the pilot is to lightly tap that end of it which is nearestthe cutting lips of the tool.` The lfeature can be used with or withouthaving the pilot mount or sub-pilot of one piece with the tool.

This invention, therefore, provides the feature of interchangeabilityfrom a minimum size compatible with strength, to a maximum size, suchthat the pilot may be a few thousandths of an inch smaller than thediameter of the cutting lips, in which case the counterbore has become areamer for the accurate finishing of the hole to its final size, .whichfeature and/or function is a valuable one.

The type of support herein is very easy to manudacture and thereforemuch cheaper to manufacture because there is no extra drilling orfitting ror threading for setscrews, as in previous devices.

Mysub-pilo-t or tapered extension can be made very hard, and it is onlysubmitted to such compression as results from driving on the masterpilot. However, the strength of the master pilot :is assured by the factthat it is surface-hardened pnly, and has a tough and stronger coreunder lthe hard surface, which gives it sui'icient strength to withstandbeing driven onto the sub-pilot, and the necessary amount of flexibilityto permit it to strongly, frictionally engage when driven onto thesub-pilot. At the same time being tapered it is readily driven off orremoved from the subpilot by a light, snappy blow with a hamer and/orscrew driver. n

As before explained, because of various manufacturing requirements, thesame maximum diameter of counterbore portion or lips is often re-Iquired for a variety of screw holes of different sizes. For example,consider several screws, all {having heads one inch in diameter, buteach havting a shank of a diiferent diameter ranging from 5/8 of an inchto of an inch. It will be seen that for the same diameter or cuttingarea replresented by the letter E in Figure 2, any one of the pilots I6,II and I8 can be substituted on mount I0. The dimension E corresponds inthe example to a head which is one inch in diameter and the elements I6,I'I and I8 correspond to shank sizes ranging from 5A; of aninch to of aninch.

The present invention can be applied to any tool which uses a pilot. Forexample, it can be used in or for a spot-facing tool. The principaldifference between counterboring and spot-facing involves dimensions andproportions. Counterboring provides a recess which receives generallythe entire head of a screw. Spot-facing provides, in relation to a boredhole, a circular, flat area concentric with and surrounding the hole atthe surface. Generally the diameter of the .area is proportionately muchgreater than that lof the dia-meter of the hole, and is of very shallowdepth. The spot-facing tool has cutting lips and a pilot, and thisinvention assures that the spot-y '.faced area will be concentric withthe hole, and also that the flat area will be in a plane' at rightangles to the axis of the hole. In the case of a part to which a smallerpart is to be bolted, the hole is drilled for the screw and thisdrilling operation is followed by spot-facing, thus providing a flatsupporting area. By the same procedure, and more frequently, a flatsurface is provided on which the head of a cap screw may rest, and inthis case the screwis entirely above the surface. Usually incounterboring the screw head becomes flush with or below the surface.

This'invention may also be applied to a reamer. The drilled or boredhole is reamed and the reamer removes but a slight amount of material.The hole may be a few thousandths of an inch -out of round and thereamer will correct this condition, or the hole may be a few thousandthserallypdone throughout the length of the hole,

that is, all the way through the material. For example, if a trulyround, straight and accurate hole is requiredto be finished to .5000 ofan inch,

the initial operation would be to drill and/or to bore the hole to adiameter of a few thousandths less than .5000 of an inch. Then with areamer having a cutting lip diameter of .5000 of an inch, and with apilot of my invention having a diameter corresponding to the originalhole, my tool is run through the hole and reaming action is performed. l

The invention herein results in a very simple, easily manufactured,fool-proof, accurate and strong counterbore mounting, and while I claimspecifically the" tapering counterbore mount, I believe that theinvention is broader than the specic shape of the mount and believe thatI am the first to conceive of making this extension or mount integral orof one piece with the shank or tool, thereby obtaining positive rigidityand assuring concentricity between the pilot and cutting-lip diameter.The master pilots can be easily and accurately made and so made as to bepositively held only by friction, but easily and quickly removable.

It is to be noted that in order to resharpen the cutting lips, as wellas to sharpen the same at thetime of manufacture, the tool is supportedby the work-supporting centers of a grinding machine that engage thecenters 5 and I4. Inasmuch as the lips Will be subjected to manyresharpenings, and inasmuch as it is desired to maintain the specialrelation between the end of the pilot and the cutting lips, it is alsonecessary to cause the taper to follow back by re-grinding incorrespondence to the sharpening back of the lips. After thisre-grinding operation, the outer end of the sub-pilot is ground off orcut off so that it will not protrude beyond the outer end of the masteror control pilot. After this cutting-ofi` operation has occurred asuflicient number of times, the centering opening I4 disappears, and itis therefore necessary to apply the device shown in Figure 8 which Icall a centering pilot.

.This device merely has a taper which fits the taper of the sub-pilot,and has a centering depression 28 which, in conjunction with depression5, allows the proper centering in a machine. This centering orsharpening pilot can be driven onto the taper.

The wedging, attaching action of the pilot mount is a valuable feature.By making the mount tapered, the pilot, by its circumscribing,constricting and wedging action, serves to reinforce the mount, and toprovide the much desired immobility of the pilot when the tool is beinused.

I claim as my invention:

l. A tool of the counter-cutting type having extending beyond its boringend a projection which is of one piece with the tool, and a pilotelement removably mounted on said projection by means of a taperingfriction t which permits said pilot to be loosened and removed by a blowapplied against that end of it which is nearest the boring end of thetool.

2. A tool of the counter cutting type having extending beyond its boringend, a projection which is of one piece with the tool, said projectionbeing convergently tapered in the direction away from said end, and apilot element removheld thereon only by the frictional engagement withsaid projection.

3. A tool of the counter-cutting type having cutting lips and having ata point beyondy said lips at its boring end, an axial projection whichis of one piece with the tool, said projection being convergentlytapered in the boring direction of the tool, and a pilot element mountedon and having an accurate tapering lit with said projection, said pilotelement being held only by the frictional engagement of a taperingsurface with the tapering surface of the projection.

4. A tool of the counter-cutting type having extending beyond its boringend an extension which is of one piece with the tool and a pilotremovably mounted on said extension and secured thereon only byfrictional engagement of surfaces of said pilot and projection and sothat said frictional securing action can be annulled by moving saidpilot axially.

5. A tool of the counter-cutting type, having a stem having cutting lipsadapted to be sharpened by grinding in an axial direction and away fromthe boring end of the tool, said stem having of one piece therewith andat a point immediately adjacent the cutting ends of said lips apilotmounting extension, and a lpilot removably mounted on saidextension and rigidly secured thereon only by frictional action, saidpilot having its inner end occupying a predetermined position withrespect to the cutting ends of said lips, whereby as the lips are groundin an axial direction to sharpen them, the extension can also becorrespondingly ground axially in order that the inner end of the pilotshall always occupy said predetermined relation to said lips aftersharpening of the same.

6. A counterboring tool having, extending beyond its cutting end and ofone piece with the shank of the tool, an outwardly convergently taperedpilot mount adapted to receive and wedgingly detachably cooperate with acorrespondingly tapered opening of a pilot element.

7. A one-piece counterbore having cutting portions Which face and cut inan axial direction only, and having extending beyond those cuttingportions a pilot-mounting projection which is of one piece with thetool, and a pilot element as a separate piece removably but rigidlymounted on said projection.

8. A one-piece counterbore having cutting portions which face `and cutin an axial direction only, and having extending beyond those cuttingportions a pilot-mounting projection which is of one piece with thetool, and a pilot element as a separate piece removably but rigidlymounted on said projection, said pilot having its inner end adjacent butspaced from said cutting portions in an axial direction.

9. A one-piece tool ofthe counter-cutting type having a stem and cutterelements extending radially beyondthe stem and extending longitudinallyof the stem and having cutters which -face and cut only in an axialdirection, said tool having extending beyond said cutters a pilotmounting projection which is of one piece with' the tool and a pilotelement as a separate piece removably but rigidly mounted on saidprojection.

OSCAR C. I-IEDIN.

